The Transient Receptor Potential (TRP) superfamily is one of the largest ion channel families and consists of diverse groups of proteins. In mammals about 28 genes encode the TRP ion channel subunits. The mammalian TRP superfamily comprises six subfamilies known as the TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPML (mucolipins), TRPP (polycystin) and the TRPA (ANKTM1) ion channels1-4.
The TRPC subfamily consists of seven proteins named TRPC1 to 7 which can be further divided into four subgroups based on their sequence homology and functional similarities: 1. the TRPC1 2. TRPC4 and TRPC5 3. TRPC3, TRPC6, TRPC7 4. TRPC2.2,5 They are highly expressed in the central nervous system and to a lesser extent in peripheral tissues.
TRPC4 can form heterotetramers with TRPC1. TRPC4, TRPC1 and TRPC5 can be activated either by Ca2+ store depletion or by GPCR stimulation pathways and are also assumed to form components of store operated channels in some cell types such as salivary gland cells, endothelial cells and vascular smooth muscle cells6.
